Mobile electronic devices, such as smartphones, tablets, and smartwatches are in wide use in the world today. Such electronic devices typically employ a touch sensitive display for both data display as well as to receive user input. Most of these touch sensitive displays utilize capacitive touch sensing.
A typical touch sensitive display includes a display layer constructed from technology such as LCD, IPS, or AMOLED, as well as a sensing layer. A transparent layer is adjacent to and spaced apart from the display layer. A typical sensing layer includes a plurality of parallel drive lines, and a plurality of parallel sensing lines. The sensing lines capacitively intersect the drive lines. In operation, a single drive line is driven with a wave, such as a square wave or sine wave. The capacitance between the sensing lines and the driven drive line is sensed at the point where they intersect. Presence of a human finger or a conductive object such as a passive stylus alters the expected capacitance at the intersection point, and by measuring the change in capacitance, a touch between the finger or conductive object and the touch sensitive display can be detected.
Using current techniques, accurately determining whether a passive stylus is touching or hovering over a touch screen can be difficult due to the small size of the tip of the passive stylus. Therefore, further development in this area is desired.